- Explain how scarcity turns economic decisions into trade-offs and constrained optimization problems.
- Identify the opportunity cost of a choice as its next-best forgone alternative.
- Describe why economists use simplified models and distinguish intuitive, graphical, and mathematical understanding.
- Interpret demand, supply, and market equilibrium in a basic market graph.
- Separate positive analysis from normative analysis.
- Compare a capitalist economy with a command economy and outline the course's path from markets to their limitations.
Microeconomics, Scarcity, and Choice
Microeconomics examines how people and firms choose among alternatives when their resources are limited.
Microeconomics studies the decisions made by individuals and firms in conditions of scarcity. Time, money, and productive resources are limited, so choosing one possibility means surrendering another.
Economists represent these decisions as constrained optimization. A person, household, or firm seeks the best attainable result while respecting its limits. A consumer may face a budget, while a producer may be restricted by technology and input costs.
Recognizing Opportunity Cost
Both action and inaction carry opportunity costs. The relevant cost is not every imaginable alternative, but the best alternative that the decision rules out.
- Buying a shirt may require giving up the pants that could have been purchased instead.
- Using an evening to watch television may mean foregoing work and the wages it would have produced.
- Sleeping late sacrifices whatever could otherwise have been accomplished during that time.
This focus on unavoidable costs helps explain the description of economics as the “dismal science.” Yet the idea is practical rather than merely gloomy: noticing the alternative being surrendered can improve a decision.
What is forgone by spending four years in college? Include both monetary and non-monetary alternatives.
Possible costs include tuition and other spending, along with the earnings, work experience, time, and alternative activities given up during those years.
Using Models in Economics
Economic models sacrifice complete realism to make broad relationships understandable and usable.
Unlike universal laws in the hard sciences, economic models are not completely accurate descriptions of every case. Their simplifying assumptions aim to explain large patterns through a manageable number of steps.
George Box summarized the point by observing that models can be incorrect in a literal sense and still be useful. Economists therefore balance realism against tractability, often favoring a model that is simple enough to teach and apply while remaining broadly informative.
- Intuitive understanding: explain the model clearly in ordinary language. This is the most important level.
- Graphical understanding: use an x-y graph to communicate substantial information compactly.
- Mathematical understanding: express the model with equations for precise manipulation and testing, even though this level contributes less to intuition.
The Supply-and-Demand Model
Market outcomes depend on the interaction of buyers' demand and producers' supply.
The first major microeconomic model is supply and demand. Adam Smith presented the water-diamond paradox in his 1776 bookThe Wealth of Nationsto show why both sides of a market matter.
Reading a Supply-and-Demand Graph
For a market in roses, place the number of roses on the x-axis and the price of each rose on the y-axis. The graph then contains a demand curve and a supply curve.
- The usually downward-sloping demand curve records how many roses consumers wish to purchase at each price. A higher price is associated with a smaller desired quantity.
- The usually upward-sloping supply curve records how many roses firms will produce at each price. A higher price makes production more profitable and encourages a larger supplied quantity.
This introductory picture leaves open where the curves originate and how equilibrium is reached. Later analysis builds both curves from first principles.
Recall one real price change that appeared to result from changing demand rather than changing supply. Then identify an example that appeared to result from changing supply.
Positive and Normative Economic Analysis
Positive analysis explains what happens, whereas normative analysis asks what ought to happen.
- Positive analysis examines how things are by describing relationships that can be tested. For example: if gasoline becomes more expensive, people will purchase less gasoline.
- Normative analysis addresses how things should be and therefore includes opinions or value judgments. For example: the government ought to tax gasoline to reduce pollution.
An early eBay auction illustrates the distinction. A seller offered a kidney, bids rose from 5 million, and the auction was then stopped.
- The positive question asks why bidding reached such a high level. Very few people are willing to sell a kidney, while many people need transplants to survive. Low supply combined with high demand accounts for the high price without making a moral judgment.
- The normative question asks whether kidney sales on eBay ought to be permitted. Facts alone cannot settle this because the answer depends on ethics, values, and ideas of fairness.
Why Restrict Kidney Sales?
The initial economic case for allowing a sale is that both participants could gain. The recipient survives, while the seller receives a potentially life-changing payment; most people can live healthily with one kidney. The objections fall into three groups.
- Market failures: circumstances that stop a market from operating efficiently.
- Equity or fairness: a market could allocate kidneys by wealth rather than by medical need.
- Behavioral economics: people may depart systematically from perfectly rational decision-making.
- Fraud may prevent buyers from knowing whether a kidney is genuine and healthy.
- Imperfect information may leave sellers unaware of the long-term risks of living with one kidney.
- Externalities may arise if a seller's family bears harm when something goes wrong, even though that cost is outside the sale.
At present, donated kidneys are assigned through a waiting list that gives priority to medical need rather than wealth. Open sales would likely reserve access for richer buyers, producing an allocation society might regard as unjust.
People can also act impulsively, misread probabilities, or respond to immediate desperation. Someone in poverty might sell a kidney without adequately weighing later consequences, even when the relevant information is available. Behavioral economics studies these patterned departures from rational choice.
Market and Command Economies
Capitalism decentralizes decisions, while a command economy assigns them to government.
Moving beyond one market raises a broader question: how much freedom should an economy have? Capitalism and the command economy provide two opposing models.
The Capitalist Economy
Capitalism has generated enormous growth. Over roughly 150 years, the United States developed from a relatively poor country into the world's wealthiest and most powerful nation, largely through its capitalist system.
The same system can produce serious inequality. Among major developed countries, the United States has exceptionally unequal income distribution: the top 1% receives a particularly large share, leaving the bottom 99% with a smaller share than their counterparts elsewhere. Pollution, financial crises, and other difficulties may also occur even when decentralized markets operate efficiently.
The Command Economy
Under this model, officials decide how many cars, shirts, CDs, and other products will be made and who will receive them, perhaps through queues or political membership. The Soviet Union before 1989 was the central example.
Although the theory promised equitable access to goods, the system performed very poorly in practice. Central control created opportunities for corruption without natural checks. Lacking market prices that reveal what people want, planners produced unsuitable quantities and products. Ignoring people's preferences contributed to dissatisfaction and economic collapse.
Smith's central insight is that decentralized market choices match output to people's desires more effectively than a central planner can. This helps explain why capitalism, despite its defects, has been more successful at producing wealth.
The Route Ahead
The next task is to explain how self-interested consumers and firms can produce an outcome that benefits society without central direction. The initial working meaning of social benefit is maximum surplus: producing the greatest amount of output that people value.
- Begin with demand by studying how consumers choose what to buy within their budgets.
- Turn to supply by studying how firms select inputs and decide what outputs to produce.
- Compare perfectly competitive markets, Smith's ideal, with monopoly markets dominated by one firm.
- Combine demand and supply to understand market equilibrium and the operation of the invisible hand.
- Finally, investigate where that mechanism fails through market failures, equity concerns, behavioral issues, and related factors.
Common misconceptions
Watch out: Opportunity cost consists only of money paid for a choice.
Instead: It is the value of the next-best forgone alternative and may include money, earnings, time, experience, or other activities.
Watch out: Demand alone, or supply alone, is enough to explain a market price.
Instead: Market outcomes depend on supply and demand acting together, as the water-diamond paradox demonstrates.
Watch out: A factual economic explanation can by itself determine what society should permit.
Instead: Positive analysis explains what happens; a normative conclusion also requires ethical values and judgments about fairness.
Lesson recap
- Scarcity makes choice unavoidable, so microeconomics centers on constrained decisions and trade-offs.
- The opportunity cost of a decision is its next-best forgone alternative.
- Economic models use simplifying assumptions to exchange perfect realism for useful, tractable explanations.
- Supply and demand jointly explain market outcomes, and their intersection identifies equilibrium.
- Positive analysis describes what happens; normative analysis evaluates what should happen.
- Capitalism uses decentralized decisions and the invisible hand, while a command economy relies on government production and allocation decisions.